Generally, in a rotor of a rotating electrical machine, a rotor yoke is formed by stacking a plurality of steel plates formed in a substantially annular shape and a plurality of magnets forming magnet pole sections are embedded in an outer circumferential side of the rotor yoke. In recent years, to reduce heat generation of a magnet due to high output of a rotating electrical machine, a rotor yoke is provided with a cooling passage for cooling the rotor from inside.
An electric motor in which a cooling passage extending in an axial direction is provided in a rotor yoke in which a plurality of magnets are embedded and the rotor yoke is cooled by a coolant flowing through the cooling passage, and then the coolant is discharged from a hole provided in an end plate has been disclosed in JP-A-2011-223717.
A technique in which, in a rotor of a rotating electrical machine, to equalize distortion and magnetic characteristics of steel plates when a rotor yoke is manufactured, a core block constituted by stacking a plurality of steel plates is assembled by rotating the core block (hereinafter, also referred to as “being skewed”) by a predetermined angle has been known.
However, in a rotor of an electric motor of the related art, when core blocks are skewed, there is a possibility that a coolant reservoir is caused between the core blocks and in a cooling passage formed in a rotor yoke and the coolant cannot be completely discharged and may remain in the cooling passage. The coolant staying in the cooling passage becomes a cause of imbalance of the rotor and there is a possibility that vibration may occur due to the imbalance when the rotor operates.